A prophetic "warning to humanity" giving notice of perils facing the Earth has been issued by more than 15,000 scientists from around the world.

Climate change, deforestation, loss of access to fresh water, species extinctions and uncontrolled human population growth are all threatening mankind and the Earth's future.

The letter, originally written in 1992 and signed by 1500 scientists, argued human impacts on the natural world were likely to lead to "vast human misery" and a planet that was 'irretrievably mutilated'.

But a quarter of a century since a majority of the world's living Nobel Laureates united to sign a warning letter about the Earth, the global scientific community's view of the future is even more bleak.

Dead trees stand in a recently deforested section of the Amazon rainforest. Climate change, deforestation, loss of access to fresh water, threaten mankind's future, scientists say. Photo / Getty
Dead trees stand in a recently deforested section of the Amazon rainforest. Climate change, deforestation, loss of access to fresh water, threaten mankind's future, scientists say. Photo / Getty

The message, posted online, updates an original Warning from the Union of Concerned Scientists and around 1700 signatories delivered in 1992, the MailOnline reported.

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Apart from the hole in the ozone layer, which has now been stabilised, every one of the major threats identified in 1992 has worsened.

Runaway consumption of precious resources by an exploding population remains the biggest danger facing humankind, say the scientists.

In the second warning letter to the globe, more than 15,000 scientists from 184 countries said humans had "unleashed a mass extinction event, the sixth in roughly 540 million years, wherein many current life forms could be annihilated or at least committed to extinction by the end of this century".

In the second warning letter to the globe, more than 15,000 scientists said humans had 'unleashed a mass extinction event, the sixth in roughly 540 million years'. Photo / 123rf
In the second warning letter to the globe, more than 15,000 scientists said humans had 'unleashed a mass extinction event, the sixth in roughly 540 million years'. Photo / 123rf

People should eat less meat, have fewer kids, consume less and use green energy to save the planet, the world's leading scientists urged.

"We are jeopardising our future by not reining in our intense but geographically and demographically uneven material consumption and by not perceiving continued rapid population growth as a primary driver behind many ecological and even societal threats", it said.

"By failing to adequately limit population growth, reassess the role of an economy rooted in growth, reduce greenhouse gases, incentivise renewable energy, protect habitat, restore ecosystems, curb pollution, halt defaunation, and constrain invasive alien species, humanity is not taking the urgent steps needed to safeguard our imperilled biosphere."

It used data from governments, charities and individual researchers to warn of a "substantial and irreversible harm" to the Earth.

They said the reduction in ozone-depleting chemicals and an increase in energy generated from renewable sources were a positive step.

There has also been a rapid decline in the number of children women are having as education levels increase and the rate of deforestation in some regions has also slowed.

But now it required the public to pressure their political leaders to take more decisive action.

This could include more nature and marine reserves, tougher laws to stamp out poaching and trade in wildlife, better family planning and educational programmes, more vegetarianism and less food waste, and massively adopting renewable energy and other 'green' technologies.

Professor William Ripple at Oregon State University said: "Some people might be tempted to dismiss this evidence and think we are just being alarmist.

"Scientists are in the business of analysing data and looking at the long-term consequences."

By 2030, up to 170 million hectares of forest - equivalent to the combined size of Germany, France, Spain and Portugal - may be lost, experts from WWF have previously warned. Photo / WWF
By 2030, up to 170 million hectares of forest - equivalent to the combined size of Germany, France, Spain and Portugal - may be lost, experts from WWF have previously warned. Photo / WWF

He said that those who signed this second warning aren't just raising a false alarm.
'They are acknowledging the obvious signs that we are heading down an unsustainable path', Dr Ripple said.

"We are hoping that our paper will ignite a wide-spread public debate about the global environment and climate."

The article "World Scientists' Warning to Humanity: A Second Notice" notes 25 negative global trends.

These include a 26 per cent reduction in the amount of fresh water available per capita, a drop in the harvest of wild-caught fish, despite an increase in fishing effort and a 75 per cent increase in the number of ocean dead zones.

There has also been a loss of 300 million acres of forestland, much of it converted for agricultural uses and a collective 29 per cent reduction in the numbers of mammals, reptiles, amphibians, birds and fish.

There are continuing significant increases in global carbon emissions and average temperatures, a 35 per cent rise in human population.

But if there is the will, mankind can move the Earth's systems toward sustainability.
The authors said: "To prevent widespread misery and catastrophic biodiversity loss, humanity must practice a more environmentally sustainable alternative to business as usual.

This prescription was well articulated by the world's leading scientists 25 years ago, but in most respects, we have not heeded their warning.

"Soon it will be too late to shift course away from our failing trajectory, and time is running out.

"We must recognise, in our day-to-day lives and in our governing institutions, that Earth with all its life is our only home.

"We can make great progress for the sake of humanity and the planet on which we depend."

University of Auckland Associate Professor Mark Costello, a lecturer in biogeography, was among the 15,364 signatories of the letter.

Costello said he signed the warning as he agreed with its principles.

"New Zealand has already been looking at these things, it's not radical... We know what's good for us, but we need self discipline and for the government to take that action."

He explained New Zealanders should care about the warning as "we're partly responsible for it, it will affect generations to come".

- Additional reporting NZ Herald